1. Field of the Invention
The present invention relates to an improved outboard motor with an intake silencer.
2. Description of the Related Art
Intake noise caused by outboard motors without intake silencers or outboard motors with intake openings directed to the hulls to which they are mounted, is transmitted directly to operators. To prevent it, outboard motors have been provided with intake silencers in the passage of intake air to reduce intake noise. An outboard motor with such an intake silencer is disclosed, for example, in Japanese Patent Laid-Open Publication No. HEI-8-310487.
This outboard motor has an intake silencer interposed in the induction system of an engine. The induction system has a throttle body arranged in the laterally and generally middle part in the front portion of an engine room in the outboard motor, and takes air in from both right and left sides of the throttle body. Thus the total cross-sectional area of two intake openings of the intake silencer is greater than the cross-sectional area of the intake air passage of the throttle body, securing a sufficient amount of intake air.
The above conventional intake silencer is arranged to face the hull (in the front portion of the outboard motor in the advancing direction), and the intake openings face upwards in the vertical direction, so that intake noise is directly transmitted to an operator, resulting in an unsatisfactory endeavor in the reduction of intake noise.
The present invention was made with the above points in mind and it is accordingly an object of the present invention to provide a V-engine-mounted outboard motor in which intake noise is prevented from being directly transmitted to an operator without making the outboard motor larger.
According to the present invention, there is provided an outboard motor comprising: a V engine arranged in a horizontal direction, the engine comprising: an engine block comprising two cylinder blocks extending in a V configuration, forming an opening to the rear of the outboard motor, and a skirt integrally formed with the cylinder blocks and housing a crankshaft arranged vertically; and two cylinder heads having a plurality of combustion chambers, being provided at the rear ends of the cylinder blocks; and an intake silencer comprising: two inlets positioned above the cylinder heads and opening rearwards of the outboard motor for taking air in; and one outlet positioned between the two inlets for letting the inlet air out to supply it to the combustion chambers.
Thus in the present invention, the V configuration of the V engine mounted to the outboard motor is utilized to sufficiently secure the volume of an expansion chamber and the opening of the intake silencer while making the lateral dimension of the intake silencer smaller than that of the opening end of the V configuration. The two inlets open rearwards of the outboard motor so as to prevent intake noise from being directly transmitted to an operator, thereby increasing the noise dampening effect of the intake silencer. Further, since upper space of the engine block is utilized to arrange the intake silencer therein, the dimension of the outboard motor in the back and forth direction is made smaller, making the outboard motor compact. Furthermore, since the two inlets are provided, a cross-sectional area of each inlet is made smaller, saving space.
The outboard motor further comprises a transmission system for transmitting drive force from the crankshaft to a camshaft for opening or closing intake valves and exhaust valves provided in the combustion chambers, the transmission system being provided between the engine block and the intake silencer.
Thus, since the intake silencer is arranged above the transmission system provided above the engine block, space above the transmission system is usable, making the outboard motor compact.
It is preferred that a throttle body connected to the outlet of the intake silencer be arranged between the cylinder heads extending in a V configuration above the camshaft of the transmission system so that space is efficiently utilized without waste. The outlet of the intake silencer is connected to the throttle body via a grommet in an embodiment, for example.
In the present invention, the intake silencer has a body with a top wall configured flat. Thus the height of the intake silencer is made smaller, resulting in the smaller height of the outboard motor.